Fuel injection nozzle for a gas turbine engine



Aug. 14, 1962 R. CHUTE ETAL 3,048,915

FUEL INJECTION NOZZLE FOR A GAS TURBINE ENGINE Original Filed May 12,1958 tea atent fine 3,d4d,9l5 Patented Aug. 14:, 1962 3,048,315 FUELlNJECTlUN NOZZLE FUR A GAS TURBINE ENGWE This invention relates to anair-fuel atomizing nozzle adapted to be used with a gas turbine liquidfuel control system. The present application is a division of copendingapplication Serial No. 734,637, filed May 12, 1958, now Patent No.2,945,629.

Various types of fuel-air atomizing nozzles available to the art areeffective to provide a combustible spray pattern of liquid fuelparticles. Such nozzles require either fuel and air pressures ofconsiderable magnitude or a large air mass flow if the air pressure isreduced. The size and capacity of the fuel-air pumping unit must becorrespondingly large. Further, wwhen the nozzle is used with a gasturbine fuel control system, the operating speed range throughout whichadequate fuel dispersion can be obtained is undesirably narrow.

Certain of the prior art nozzles are provided with an internal mixingchamber within the nozzle assembly to facilitate the mixing of air andliquid fuel. A considerable restriction is encountered by the fuel-airmixture before it is discharged into the combustion chamber associatedwith the nozzle. The unfavorable characteristics of such nozzles arebelieved to be due in part to the fact that mixing of the fuel and airtakes place internally of the nozzle assembly.

These and other disadvantages are overcome in accordance with thepresent invention by providing a new and improved nozzle whichincorporates separate fuel and air passage means having intersectingbranch portions. Air is conducted through the air branch portions and iseffective to shear or break up a controlled flow of liquid fuel Withinthe fuel branch portions at the regions of intersection of the fuel andair branch portions.

According to an important feature of the present invention, the fuelbranch portions are effective to conduct liquid fuel to an externallocation near a terminal portion of the nozzle assembly. The air branchportions are adapted to intersect the fuel branch portions in the vicinity of the nozzle terminal portion at a location which is exterior ofthe nozzle assembly. The liquid fuel is there by atomized by the airexternally of the nozzle rather than in an internal mixing chamber or ininternal nozzle passages. The resulting spray or distribution pattern iscomprised of fuel particles which are more finely dispersed than thepattern obtainable with conventional nozzles at a comparable airpressure and air flow.

in the above regard, nozzles of the internal mixing type frequentlydepend on a swirl chamber immediately preceding the nozzle dischargeorifice. The resulting fuelair spray pattern is substantially a solidcone which in certain types of turbine engines inhibits combustion ofthe fuel particies near the center of the cone and also enables anaccumulation of liquid fuel particles adjacent the exterior of thedischarge nozzle which drip and cause undesirable carbon deposits.

An object of the present invention is to achieve a substantially hollowcone fuel-air dispersion or spray pattern which not only renders thefuel more susceptible to combustion, but requires appreciably less airfor atomization than in conventional nozzles and minimizes drip ofliquid fuel from the nozzle extremity.

Another object is to provide a new and improved liquid fuel and airatomizing nozzle which is simple in construction, inexpensive tomanufacture and characterized by improved nozzle mixing properties.

Another object of the present invention is to provide a new and improvedfuel-air atomizing nozzle for use with the combustion chamber of aliquid fuel combustion apparatus, which is adapted to provide acompletely atomized spray or fuel-air distribution pattern throughout awide range of controlled variations in the rate of fuel consumption.

Another object is to provide a fuel-air atomizing nozzle of improvedefiiciency which requires relatively low fuel and air pressures and acomparatively low air mass flow with respect to conventional nozzles.

Another and more specific object is to provide an improved fuel-airatomizing nozzle structure having a cylindrical distributor elementreceived within a nozzle body. The distributor element is provided withan endwise converging conical terminal portion which extends to theexterior of the body. A plurality of fuel passage grooves extend in theouter surface of the terminal portion from within the body to itsexterior and are intersected at locations exteriorly of the body bybranch air passages which extend substantially normally to the groovesand communicate with a central air chamber within the distributorelement. The air chamber and fuel passage grooves are connected withinthe nozzle structure to sources of fuel and air respectively underpressure. In addition, a spray plate is provided which extendstransversely across the grooves in parallelism with the direction ofdischarge of air into the grooves from the branch air passages andblocks the grooves at locations adjacent and endwise of theirintersections with the branch air passages. The aforesaid air chamber islocated coaxially within the terminal portion and opens endwise toreceive the spray plate by a press fit therein. By virtue of theforegoing structure, major simplifications and economies in fabricationand assembly are enabled and an optimum atomization and a preferredspray pattern are achieved.

One of the major problems involved in the manufacture of fuel-airatomizing nozzles of the type which include intersecting fuel and airbranch passages arranged to cause shearing and atomization of the fuelas it leaves the nozzle assembly is the alignment of the aforesaidintersecting passages. Heretofore fuel passage grooves have been milledin the exterior of the nozzle distributor element. Air passages havebeen drilled into the distributor element so as to intersect the fuelpassage grooves and the central air chamber within the distributor.Considerable difficulty and expense have been encountered in maintainingthe close dimensional tolerances required, particularly at the locationof intersection of the air and fuel branch passages.

It is accordingly another object of the present invention to provide animproved and simplified method for manufacturing such nozzles, whereinthe central air chamber is formed circularly and coaxially Within thecylindrical distributor element adjacent one end thereof, and the fuelpassage grooves are milled in the exterior surface of the distributoradjacent said one end. The central circular chamber is formedsufficiently large and the grooves are milled sufficiently deep so as tointersect the chamber. Thus the branch air passages are automaticallyprovided in proper alignment intersecting the grooves so as to supplyair for shearing and atomizing liquid fuel flowing along the grooves.

The foregoing method enables the overall nozzle distributor to be forcedeconomically by automatic screw machines. The grooves can be milled atany circumferential location in the terminal portion of the distributorelement. By controlling the dimensions of the grooves and of the controlchamber, the dimensions and locations of the branch air passages betweenthe central air chamber and the fuel passage grooves are readilycontrolled. Correct alignment is thus assured without necessitatingprecise indexing of the distributor element.

Other objects of this invention will appear in the following descriptionand appended claims, reference bemg had to the accompanying drawingsforming a part of this specification wherein like reference characterdesignate corresponding parts in the several views.

FIGURE 1 is a view partly in elevation and partly in longitudinalmid-section showing a nozzle assembly and holder embodying the presentinvention.

FIGURE 2 is an enlarged end view of the distributor element and sprayplate removed from the nozzle body, taken in the direction of the arrow2 of FIGURE 3.

FIGURE 3 is a longitudinal section taken in the direction of the arrowssubstantially along the line 3-3 of FIGURE 2.

FIGURE 4 is a fragmentary view similar to FIGURE 3, with the spray plateremoved.

FIGURE 5 is an end view of the spray plate removed from the distributorelement, taken in the direction of the arrow along the line 5 of FIGURE3.

It is to be understood that the invention is not limited in itsapplication to the details of construction and arrangement of partsillustrated in the accompanying drawings, since the invention is capableof other embodiments and of being practiced or carried out in variousways. Also it is to be understood that the phraseology or terminologyemployed herein is for the purpose of description and not of limitation.

Referring to FIGURE 1, a nozzle assembly embodying the present inventionis illustrated by way of example with a T-shaped nozzle holder having acylindrical portion It) and in integral transverse bracket ll. Theportion It is provided with a central bore 12 which extends into thebracket 11 and opens at a threaded socket 13 adapted to receive aconventional fitting for attachment with a source of pressurized air.Forwardly of the bracket 11, the bore 12 opens into a cylindricalenlargement 14 which in turn opens into a still greater cylindricalenlargement 15. The latter is in communication with a fuel passage 16extending axially from portion 16 into bracket II and opening at athreaded socket l7 suitable for attachment with the source of fuel underpressure. The shoulder between the portions 14- and I5 is chamfered at18 to provide a conical seat for an annular spring type seal 19, whichmay comprise a Belleville washer.

Endwise of the enlargement 15, the bore of the cylindrical portion MI isreduced and threaded at 20 to re ceive the reduced threaded end 21 of acylindrical nozzle body 22. The latter is provided with a coaxialcylindrical opening 23 extending substantially its full length but beingrestricted slightly at its forward end by an integral conicallyconverging flange 24. Extending coaxially within the cylindrical opening23 is a cylindrical distributor element 25 having a reduced rear endportion 26 closely fitting within bore 12 rearwardly of the enlargementI4.

Within the latter enlargement, the outer wall of the distributor 25enlarges conically in parallelism with the conical chamfer 18 so as toseat against the inner portion of spring seal 19. The seal 19 is undertension yieldingly engaging the conical chamfer I8 and the adjacentconical enlargement of the distributor 25 and thus serves both toseparate the fuel passages 15 and In from the air passage 12 and also tourge the distributor 25 yieldingly forwardly against the flange 24, asdescribed below, thereby to provide means to compensate for differentialthermal expansion between the nozzle elements. The portion of opening 23around the distributor 25 comprises an annular fuel passage incommunication with passages 15, 16 to receive fuel therefrom and will bereferred to hereinafter as fuel passage 23.

The forward end of distributor 25 comprises an enlarged terminal portion27, FIGURE 3, which converges endwise conically from a shoulder 28located within the body 22 and extends to the exterior thereof. Theconical outer surface of the terminal portion 27 extends in parallelismwith the conical interior surface of flange 2 i and seats against thelatter to close fuel passage 23 except at the regions of eight grooves29 formed in the outer surface of portion 27. The number and arrangementof the grooves 29 will obviously depend on the engine fuel requirements.For larger engines, the total circumferential extent of grooves 29 willincrease until in the limiting case, a corresponding full conical fuelpassage will extend in the outer surface of portion 27. In the presentinstance, grooves 2i extend in equally spaced radial planes throughshoulder 23 so as to communicate with fuel passage 23 and also extend tothe forward extremity of terminal portion 27, FIGURES 2 and 3.

Extending coaxially through the cylindrical distributor 25 is an airpassage or bore 3% having an enlarged portion 3th: adapted to receivethe stem 31 of a spray plate described below. As indicated in FIGURE 5,the stem 31 is of elongated section having opposite cylindrical endportions 31a press fitted snugly into bore portion 30a and havingopposite flattened portions Slab provided to enable free passage of airpast stem 31 from air passage 3i) into enlargement or passage 36a.Endwise of passage 36a, the central passage of distributor 25 enlargesconically at 32,, then extends cylindrically at 33, then enlargesconically at 34, FIGURE 4. Forwardly of stem 31, the body of the sprayplate is restricted at 35, then enlarges cylindrically at 36 to providean annular air passage or chamber 38 therearound in bore portion 3%.Forwardly of the enlargement 36, the spray plate enlarges comically at39 in parallelism with the conical enlargement 34- and seats snuglythereagainst to close the endwise opening of passage Sta. Also asillustrated in FIGURE 3, the conical enlargement 32. is substantiallyparallel to the interior surface of the conical enlargement 39, therebyto provide a conical endwise diverging air chamber 48 extending frompassage 38 and opening at branch passages ttla into one of each of thegrooves 29 at a location externally of the body 22, FIGURE 1. Theperipheral portions of the conical spray plate 3% extend transverselyand substantially normally to the grooves 29 to block the latteradjacent and endwise of the branch passages 46a.

In operation of the nozzle, fuel is supplied under pressure via passages17 and 16 into enlargement I5 and thence along the annular fuel passage23 around the outer cylindrical surface of distributor element 25 to thegrooves 29, whereat the flange 24 directs the fuel endwise along thegrooves 29 to the exterior of the nozzle body. Air is supplied underpressure via conduits I3 and 12 to the bore 34} of distributor 25. Frombore 30, air passes around the flats 31b of the spray plate stem 31 andinto chamthe here 38 and as, which latter provides the branch airpassages ttla intersecting grooves 29. Air discharging from branchpassages 443a substantially perpendicularly to the direction of fuelflow along grooves 29 shears the fuel from the grooves and effects asubstantially endwise diverging air-fuel atomized spray patternexternally of the nozzle. The conical surface of the spray plate 39'blocking the grooves 29 prevents the possibility of fuel passing in thedirection of the grooves 29 beyond the region k of the branch passages4%, thereby to assure complete dispersion of the fuel and also toprevent the possibility of formation of liquid fuel droplets at theterminal portion of the distributor.

It is also to be noted by virtue of the foregoing that with theexception of the grooves 2% which are preferably milled into theterminal portion 27, the distributor element 25 with its conical endwiseenlarging chamber portions 32, 33, and 34- can be readily formed byautomatic screw machines. The grooves 29 are then milled or broached soas to intersect the cylindrical enlargement 33. However the grooves 29can'be cut or formed by any suitable method either prior to or afterformation of the bore 30 with its enlargements, or the grooves 29 can bereadily formed by a cross feed cutter of the screw machine which formsthe bore 30. It is apparent that the grooves 29 may be formed at anycircumferential location in the terminal portion 27. Thus these grooves29 may be readily formed without resort to precise indexing of thedistributor 25', as has been required heretofore. It is only essentialto control the axial dimension of the cylindrical enlargement 33 and theangles of the conical surfaces 32 and 34 in order to control the sizeand location of each branch passage opening 40a. By predetermining thegeometry of the conical surfaces 32, 34, and 39, the spray angle can bereadily predetermined, which spray angle Will remain constant regardlessof variation in volume of fuel and air fiow. By virtue of the parallelconical walls of the chamber 40, slight variations in depth of thegrooves 29 will not alter the spray angle. In consequence, a simplifiedmethod for automatically aligning the openings 46a of chamber 40 withgrooves 29 is readily obtained. After formation of the distributor 25,the spray plate 3139 is pressed firmly into the endwise opening bore 30aas shown in FIGURE 3. The distributor, spray plate, and body 22 are thenassembled with the holder 10, 11 to complete the nozzle sub-assembly.

We claim:

1. In the method of manufacturing a fuel-air nozzle, the steps ofproviding a distributor element having a forward end, forming in oneprocess a forwardly opening chamber in said forward end having aforwardly diverging conical rear wall, forming endwise extending fluidpassage grooves in the exterior of said forward end to intersect saidchamber adjacent said wall and provide branch passages defined in partby said wall and opening from said chamber into said grooves, providinga spray plate with a forwardly diverging inner surface blocking saidgrooves at locations forwardly of said Wall and closing the forwardopening of said chamber, and securing said plate in fixed position withrespect to said element with said surface spaced from said wall todefine in part said branch passages.

2. In the method of manufacturing a fuel-air nozzle, the steps ofproviding a distributor element with a forward end, forming a forwardlyopening chamber in said forward end, forming endwise extending fluidpassage grooves in the exterior of said forward end to intersect saidchamber and provide branch passages opening from said chamber into saidgrooves, providing a spray plate to close the forward opening of saidchamber and also to block said grooves at locations forwardly of saidbranch passages, and securing said spray plate in fixed position withrespect to said distributor to effect the aforesaid relationships.

3. In the method of manufacturing a fuel-air nozzle, the steps ofproviding a tubular distributor element with an enlarged forward endextending forwardly from a radially enlarged shoulder, forming in oneprocess an endwise opening annular chamber in said forward end with anannular rear wall, forming in another process grooves extending fromfront to rear in the exterior of said forward end and intersecting thespace rearwardly of said shoulder and also intersecting said chamber atthe region of said wall to provide endwise opening branch passagesconnecting said chamber and grooves, providing closure means adapted toclose the endwise opening of said chamber and to define forward wallsfor said branch passages and also to block said grooves at locationsforwardly of said rear wall, providing a body adapted to enclose theoutboard portions of said element at regions spaced from the latterrearwardly of said shoulder, to provide a passage in communication withthe rearward ends of said grooves, and closely in juxtaposition Withsaid forward end to define radially outer walls for said grooves forguiding iiuid to the intersection between said grooves and branchpassages, and assembling said body, closure means, and element to effectthe aforesaid relationships.

4. In the method of manufacturing a fuel-air atomizing nozzle, the stepsof providing a distributor element having a forwardly converging conicalterminal portion at its forward end and a cylindrical portion coaxiallyadjacent and rearwardly of the large end of said terminal portion and ofreduced diameter with respect to the latter end to provide an annularshoulder adjacent said rear end, forming in one process a circularendwise opening chamber with an endwise diverging conical wall in saidterminal portion, forming in another process grooves in the exterior ofsaid terminal portion extending generally from front and rear thereof tointersecting said chamber at the region of said wall to provide endwiseopening branch passages connecting said chamber and grooves, saidgrooves also being formed through said shoulder to intersect andcommunicate with the space around said cylindrical portion radiallyinwardly of said shoulder, providing a forwardly diverging conical sprayplate, and closing the endwise opening of said chamber by securing saidplate to said element in position to define in part said branch passagesand to block said grooves at locations forwardly of said wall.

5. In a method for manufacturing a fuel-air nozzle, the steps ofproviding a hollow nozzle body, providing a distributor elementinsertable within said body and having a terminal portion adapted toextend to the exterior of said body, forming in one process an endwiseopening chamber in said terminal portion, forming in another processfluid passage grooves in the exterior surface of said terminal portionadapted to extend from Within said body to the exterior thereof tointersect said chamber at locations exteriorly of said body and provideendwise opening branch passages connecting said chamber and grooves atsaid locations, providing closure means for closing the endwise openingof said chamber and having spray plate portions adapted to intersect andblock said grooves and define the endrnost walls of said passages, andassembling said body, distributor, and closure means so that saiddistributor extends into said hollow body with said groovescommunicating with the hollow interior of said body and intersectingsaid chamber exteriorly of said body, and so that said spray plateportions intersect and block said grooves and define the endmost wallsof said passages.

References Cited in the file of this patent UNITED STATES PATENTS1,442,814 Long Jan. 23, 1923 1,805,782 Munz May 19, 1931 2,175,310Pontius Oct. 10, 1939 2,468,824 Hughey May 3, 1949

